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We talk with Alexandra Horowitz, assistant professor of psychology at Barnard College, about her new book, Inside of a Dog: What Dogs See, Smell, and Know. This engrossing work is inspired by Horowitz’s experiences with her dog, Pumpernickel, and draws upon her own and others’ research in the field of canine cognition. This book expands our understanding of the nature of dogs and provides a channel to seeing and “smelling” the world from a dog’s point of view.

Bark: Your fascinating new book, Inside of a Dog, begins with a discussion of canine “umwelt.” Can you tell us more about umwelt and how it might affect our understanding of our dogs?

Alexandra Horowitz: The idea of umwelt, which originated with the biologist Jakob von Uexküll, is that the world of each animal is defined by how he/she perceives and acts on the world. Thus, the umwelt of humans does not include infrared light, since we have no perception of these wavelengths and cannot act based on seeing it. However, for bees, who can see infrared light, it is part of their umwelt, and they use the reflected infrared from the center of some flowers to locate nectar. The scale of objects, and their salience, also matters. In our ordinary life, we humans don’t deal on [what we call] the microscopic scale of bacteria: thus, objects that small aren’t part of our impression of “what is out there” at all. A dog’s umwelt is determined by what he can perceive, by his history, by what matters in the world to him. Humans are clearly a big part of the umwelten of dogs, but we don’t register much in the fly’s umwelt (at least, not as anything distinct from other mammals).

For dogs, we can imagine that their world is defined by their perception and action. Their perception includes being able to smell much more acutely than we can (including detecting changes in others’ hormones) and hearing within a greater range than we can. Thus, they will be able to respond to stimuli we don’t even notice. At another level, their umwelt is defined by the things they can bodily act on: They handle the world with their mouths, so the world gets divided into things-that-fit-in-the-mouth and things-that-don’t-fit-in-the-mouth—a way of seeing the world that is quite different than our own.

If we begin to understand what dogs think about, what they can see and smell (and what they can’t), I think we’ll have a better understanding of what it’s like to be a dog—the dog’s perspective, if you will. Appreciating his perspective goes a long way toward making a closer relationship (as it does between people!).

B: The dog’s amazing olfactory powers make their worldview different than ours. Can you explain why?

AH: As we go about our day, we see the world first, using vision to help make sense of the sounds (conversation, sudden honking, a nearby thud) and the smells (something rancid or sweet wafting on the air) around us. Dogs smell the world first, using olfaction to organize and make sense of what they see and hear. The richness of our visual world is matched, if not surpassed, by the richness of their olfactory world.

This leads to some profound differences in the way the world looks, which I describe at length in the book. For instance, smells deteriorate over long distances, and are carried hither and thither by currents of air. The visual scene does not change with the breeze, and with distance, only looks “more distant.” The result is that the world is mapped differently for the creature who primarily “sees” it via his nose rather than his eyes.

B: You note that dogs couldn’t really see TV in the pre-digital conversion days; the physiological reason behind this is significant—can you explain it?

AH: It has to do with how we process light. Specialized cells in the eyes of mammals translate light waves into neural activity by changing the pigment in the cells. In the milliseconds that the pigment is changing, the cell can’t receive any more light. This leads to what is called the “flicker-fusion” rate: essentially, the number of snapshots of the world that the eyes can process each second. Our flicker-fusion rate is about 60 images per second.